Why is it so much more expensive to get a photo taken by a studio and printed by a photo studio than a photo taken by a regular camera?

It depends on whether it's film or digital. The film studio shot is reversal film, the ordinary camera is the traditional film, positive development film. The color reproduction of the image of the reversal film is much better. So the price difference is big.

If it is a digital film, in addition to the material, the choice of photo paper if there is a difference. The price is also different